Resistive Instabilities and Transport Phenomena in Spheromak Plasma

理想磁流体稳定性分析是研究等离子体阻性不稳定性的重要手段。因此，我们需要用一个真实的模型来研究球面的理想MHD稳定性。为此目的进行了以下调查。我们研究了Mercier判据如何用于分析球面模的稳定性，发现它对于内模而不是扭结模是一个很好的判据。通量保持器(FC)有一个孔和一条将等离子体引入其中的管道，还有一个外部线圈来关闭FC中的所有磁性表面。用边界拟合曲线坐标系确定了这样一个复杂区域的MHD平衡位形。用Mercier判据研究了它们的稳定性。计算结果表明，外加线圈电流对等离子体的约束有较大的改善，中心导体安装在FC中的改善作用更大。实验结果表明，在外加线圈电流的作用下，所有的磁性面都是闭合的。然而，无论是否安装中心导体，等离子体的寿命都不会有明显的变化。磁场分布的测量表明，在对称轴附近存在一个区域，在那里没有发现环向磁场。我们称这一区域为通量洞(FH)。我们研究了FH对球面稳定性的影响，发现它具有稳定作用。我们做了其他的调查。例如，4.用Glasser，Green和Johnson的结果研究了球面的电阻不稳定性，5.囚禁粒子对输运现象的影响。关于细节，请参阅本助学金取得的成果报告。

The stability analysis by the ideal magnetohydrodynamic (MHD) plays an important role to investigate the resistive instabilities of a plasma. Hence, we need investigate the ideal MHD stability of the spheromak by use of a realistic model. The following investigations were made for this purpose.1. We investigated how the Mercier criterion is useful to analyze the stability of the spheromak and found that it gives a good criterion for internal modes other than kink modes.2. The flux conserver (FC) has a hole and a duct to introduce the plasma into it, and also has an external coil to close all the magnetic surfaces in FC. THE MHD equilibrium configurations in such a complex region are determined by using the boundary fitted curvilinear coordinate system. The stabilities of them are investigated by use of the Mercier criterion. As results of computations, we obtained the plasma confinement is improved considerably by the external coil current, and the improvement is larger when a center conductor is installed in FC. Experimental results show all the magnetic surfaces are surely closed when the external coil current is applied. However, the life time of the plasma does not change appreciably whether the center conductor is installed or not. Measurements of the magnetic field distribution revealed there exists a region near the symmetric axis, where no toroidal magnetic field is found. We call this region ther flux hole (FH).3. We investigated the effect of FH on the stability of the spheromak and found that it has a stabilizing effect. We made other investigations. For examples,4. the resistive instabilities of the spheromak by using Glasser, Green and Johnson's results, and 5. the effects of trapped particles on the transport phenomena. About detailed points, see the report on the results obtained by this Grant-in-Aid.